As an electro-acoustic transducer used in an electronic device, there is a piezoelectric electro-acoustic transducer using a piezoelectric vibrator. The piezoelectric electro-acoustic transducer generates a vibrational amplitude by using an expansion and contraction motion of the piezoelectric vibrator. Thus, there is an advantage in a reduction in the thickness thereof as compared with an electrodynamic electro-acoustic transducer constituted by a magnet, a voice coil, or the like. A technique involved in the piezoelectric electro-acoustic transducer is disclosed in, for example, Patent Document 1. In the technique disclosed in Patent Document 1, a base to which a piezoelectric element is attached is connected to a supporting member through a vibrating film having a lower rigidity than the base.
In addition, the piezoelectric vibrator is also used as, for example, an ultrasound wave sensor. A technique disclosed in Patent Document 2 relates to the ultrasound wave sensor using the piezoelectric vibrator, and discloses that an outer circumferential edge of a metal plate that vibrates flexurally in association with an expansion and contraction vibration of a piezoelectric member is held by a holding member.